Many applications require the use of robotic arms or other means to pick up an item, hold that item, and move it to another location. For example, in semiconductor or solar cell manufacturing, it is common to use a gripper to pick up one or more wafers, and move those wafers to another location. For example, unprocessed wafers may arrive at a site in a carrier. These unprocessed wafers must be transferred to another carrier or holder so that they may be processed. After being processed, these wafers must again be picked up and moved to a carrier for processed wafers.
There are various techniques currently used to pick up and hold items. FIG. 1 shows a typical suction system 10 utilizing a Venturi device 40. Compressed Dry Air (CDA) arrives from a source 20. When gating element 30, which may be a valve, is actuated, CDA rushes from the source 20, passing through the Venturi device 40 and exiting through the muffler 50 into the environment. Note that muffler 50 is optional in all Venturi device based embodiments shown in this disclosure. The Venturi device 40 creates negative pressure in conduit 60, which forces air into the suction system, thereby evacuating the cavity 70 in communication with the conduit 60. These suction systems 10 generate a great amount of negative pressure, and are therefore effective for picking up items 90 located below gripper 80. However, while these suction systems 10 excel at picking up items 90, they require a continuously flow of CDA in order to retain the item 90 once picked up. In some instances, a single gripper 80 may require 4 cubic feet per minute (CFM) of CDA to pick up and retain an item 90. Therefore, for large systems, or those with very high utilization, the amount of CDA used may be excessive and cost prohibitive.
FIG. 2 shows a typical suction system 100 utilizing vacuum. In this system, a negative pressure source 110 is used. A gating element 120, such as a valve, is used to actuate this system. When the gating element 120 is in a first position, the negative pressure source 110 is in communication with the cavity 130, thereby creating negative pressure in the gripper 140. If an item 90 is placed at or near this gripper 140, the suction system 100 can retain the item 90. However, due to the low differential pressure, vacuum systems may not be ideal in picking up items, such as semiconductor wafers, without initial contact. However, vacuum systems are relatively cost effective, in comparison to the Venturi device based suction system 10 described in FIG. 1.
When the gating element 120 is in a second position, the negative pressure source 110 is disconnected from the gripper 140, thereby releasing the item 90. In some embodiments, a source of CDA 150 is provided in series with a second gating element 160, which also may be a valve. When the gating element 120 is turned to the second position, the second gating element 160 may be opened. This supplies CDA to the gripper 140, which forces the item 90 away from the gripper 140.
In some embodiments, there may be a requirement to pick up (without initial contact), hold and place a large number of items. One such embodiment may be a semiconductor or solar cell manufacturing process. The use of vacuum systems is cost effective, but is not optimal in picking up a large number of items. Venturi device based suction systems are very proficient at picking up items quickly and effectively without initial contact for a seal to be formed, but may be cost prohibitive at a large scale due to the amount of CDA needed.
Thus, it would be beneficial if a suction system existed which was cost effective and had the ability to pick up items quickly without initial contact. Furthermore, it would be beneficial if there were a large scale system capable of picking up, holding and placing large numbers of items in a relatively short period of time.